The present invention relates to a procedure and an apparatus for the control of elevator doors.
The function of an elevator is to provide a certain transport capacity for the transportation of passengers between the floors of a building. The capacity should be as high as possible. It depends on the number, dimensions and travelling speed of the elevator cars. For the transport capacity to be efficiently exploited, the time the elevator spends standing at a floor should be as short as possible, i.e. only as long as is necessary to allow the passengers to leave the car and new passengers to enter. All time in excess of this is dead time, during which the elevator cannot move and no passengers are entering or leaving the car.
The operation of the door control system is of great importance in the utilization of the transport capacity, because the better the door control procedure, the sooner the doors can be closed after the last passenger has entered/left the car and the more effectively is the transport capacity of the elevator utilized. On the other hand, if the doors are closed too soon, a passenger may be caught between the doors. In principle, this involves no danger, because the safety circuits will reopen the doors. However, this is an unpleasant experience for the passenger, and it also means wasting time as it disturbs the normal movement of passengers and reopening the door takes its own time.
In a previously known procedure, the movement of a passenger into or out of an elevator car is detected by means of a light beam passing between the door posts. When the passage of a passenger into or out of the car is detected from an interrupted light beam, the door is kept open for a certain delay in case another passenger should follow. This system has obvious drawbacks: the delay is dead time and should therefore be minimized. However, the delay cannot be shortened without limit because the behaviour of the door would then become aggressive as the door would tend to close too soon, jamming the next potential passenger in the doorway. The method is a mixture of a real time procedure and a statistical one: the passengers are observed in real time but the action (delay) triggered by them contains an implicit idea of normal passage of passengers and a normal preset mean distance between them during the movement.
Publication EP A2 452 130 presents a procedure whereby the door-open time is estimated on the basis of history data. The operation is based on counting and keeping floor-specific statistics of the numbers of passengers entering and leaving the elevator car. The history data are used for the determination of the door-open time for each hour of the day. As the procedure depends heavily on statistics, it cannot take the momentary situation prevailing around the door into account.